Polyacetal resin is one of the typical engineering plastics having outstanding mechanical-strength, heat resistance, and chemical resistance properties. It finds general use as parts of automobiles, household electric appliances, and precision machines.
Molded parts formed of polyacetal resin when used for such purposes are usually assembled with other components by press fitting or staking. However, the parts may be bonded adhesively to one another or to components formed of metal, glass, or any other materials. The bonding of part (such as automotive parts which are subject to vibration and considerable temperature change is, in particular, accomplished by the aid of a curable reactive adhesive such as an epoxy resin or a silicone resin.
The molded products of polyacetal resin have outstanding chemical resistance owing to their inert surface. On the other hand, they often exhibit poor adhesion properties with adhesives. To cope with this situation, they usually undergo pretreatment, for example, surface treatment (surface roughening) with corona discharge, UV light irradiation, or acid etching, or primer coating onto the surface of the resin, prior to bonding with an adhesive. However, pretreatment of polyacetal resin parts increases the complexity of the production process which, in turn, can increase production costs.
The foregoing problems have led to a demand for suitable adhesives for polyacetal resin as well as a polyacetal resin having a greater affinity for adhesives. However, nothing to meet this demand has thus far been proposed.
The present invention is directed toward a new polyacetal resin composition which yields molded products capable of bonding firmly with a curable reactive resin adhesive (such as epoxy resin adhesive or a silicon resin adhesive) without needing of any surface pretreatment. In this regard, the polyacetal resin composition according to this invention achieves such a result by virtue of the incorporation of an isocyanate compound or an isothiocyanate compound.
More specifically, the present invention is embodied in a polyacetal resin composition which comprises a polyacetal resin (as component A) and one or more members selected from the group consisting of an isocyanate compound, an isothiocyanate compound, and a modified product thereof (as component B) in an amount of 0.1-15 wt % of the composition. The polyacetal resin composition adhesion properties when bonded with a curable reactive resin adhesive.